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Cartridge loading for dummies

B

banjoman

pfm Member
After a blissful period with my 2M Black and Croft 25R phono, I have thrown myself into the minefield of MC cartridges and lots of different phono stages.

I am playing with different carts with different loading suggestions (Benz Wood SL, Clearaudio Insider, AT33PTG).

However, since all the phono stages I am interested in and playing with now are limited in the range of loading options, I've realised I really have no clue on how this whole cartridge loading thing really works.

Hence, appreciate some dummies answers to my dummies questions:
- The default MC setting for most phono stages is 100 ohm. Does this include the capacitance effect of the phono cable and the tonearm wiring, or are these things largely immaterial for loading?
- Does the same apply when I change loading to - say 1000 ohm?
- When I had the Arkless phono stage, JEz gave me a bunch of loading plugs for different settings. Can I use similar loading plugs for different settings (250/500/1000 ohm) in a phono stage set to 100 ohm to get more loading options?
 
I'm no expert on this, but I understand that capacitance is largely irrelevant to m/coils (but important for m/magnets); useful if you suffer from RFI, though :).

The default setting of 100 ohms is probably because few if any m/coil cart's like to see below this (my Koetsus and Transfig. Proteus do like 100 ohms). My Benz Ebony prefers 200 plus, and my old Lyras liked 500 plus. From various threads on this, both tastes and partnering kit largely determine the resistance range effective for optimum sonic performance.

I have a Superline with 3 standard plugs, and by experience I wouldn't have an 'all things to all cart's' phono stage, though (like my previous Prefix), they can be extremely accommodating.
 
Loading is less critical with MC carts. 100 Ohms is the normal value and capacitance is of far less if any significance. To use a low output MC cart with the Croft phono stage you'll obviously need a step-up transformer.
 
Also don't forget that high output MCs require a higher load resistance usually around 1K to 47K Ohm.

Remember that MC carts have a very wide bandwidth and due to the inductance and capacitance will have a resonance (peak) in the very high frequencies. The loading resistance is to damp that resonance so that you have a 'flat' response over the frequency range.

Lower inductance types are more critical but higher inductance carts may need little if any tuning. Unfortunately the inductance of an MC cart is rarely given.

My phono stage has an input of 600 Ohm and I've used it successfully with a Troika (recommended 470 Ohm load) and a much more expensive DRT XV1-S with 18 micro Henry inductance (recommended >30 Ohm load) successfully. I rather expected to have to change the phono stage but it appears that the better cart isn't fussy.

Cheers,

DV
 
For perhaps 95%+ of MC cartridges the source impedance is <10 Ohms with inductance <5mH.
This makes them largely bullet proof in terms of loading and you should hear no difference in sonics due to loading unless the load is particularly low impedance and well <100 Ohms.
Capacitance on MC stages should never be high enough to impact response near the audio band.

This is for active gain stages.

For SUTS the loading needs more careful matching though again the audible effects tend to be small and confined to the very highest frequencies.

I've found very low impedance loading at <10 Ohms has the greatest effect on sonics, party because you start to see electro mechanical damping of the cartridge generator in much the same way as damping factor impacts a loudspeaker.
 
Cartridge loading recommended by the cartridge manufacturer is what the cartridge manufacturer recommended when using "their" turntable, "their" tonearm, "their" phono stage, "their" amplifier system and "their" loudspeakers in "their" test/listening room. It is not exact, only a recommendation based on what they heard in "their" test system. The upshot is it will be different/slightly different in everyone else's system.

If you have a solid state MC phono stage then selecting different resistive loadings can help "adjust" a cartridges response, particularly if it is hot in the treble (as most MC's have a rising HF response), but that is the only way you can make adjustments with solid state (putting a resister directive across the cartridge input) unless it is a MM stage and you connect an SUT in line.

With valve or tube electronics it more usual to use an SUT, and in this case the most important thing is to select the correct amount of gain for the cartridge to work correctly into the phono stage. Unless the cartridge has an extremely low internal impedance (usually have very low output too) then around 20dB of gain is sufficient (470 ohms load) for most MC's. Alternatively 26dB of gain (118ohms load) works well for lower output MC's and both will be fine for about 99% of MC cartridges.
Note: loading shown with SUTs is based on a phono stage input impedance of 47K ohms.
 
Sensible observations so far; my own mucking-about over the years has suggested that most MCs are not so very fussy. Indeed, if you use a preamp with variable loading, you will often find that higher loading, up to 47K, simply results in a slightly higher output and a slightly brighter sound.
100ohms is a pretty good general setting. I wouldn't lose sleep over this issue, it is the sort of thing (like VTA) which plays to our obsessive sides.
 
Rob and Graham,

Thanks for those clear explanations. Does that mean that adjustable cartridge loading for MCs is unnecessary for the majority of MC cartridges? If that's the case, do extra dip switches on some manufacturer's MC phono stages just add in another unnecessary switch in the signal path, with a consequent degradation in SQ?

Thanks

Charlie
 
Thanks all - that does help getting my head around it

Tony L - not planning on using the Croft with MC carts but playing with different tube and solid state MC phono stages.

I do find a difference in sound between 100ohm and 1000ohm settings on a Trichord Delphini with my Benz Wood SL. Not night and day - but noticeably clearer treble response and dynamics at 1000ohm. Which makes me think what it might be like at 500 ohms for example.

Glad to hear that in general its not such a big deal
 
G T Audio said:
Cartridge loading recommended by the cartridge manufacturer is what the cartridge manufacturer recommended when using "their" turntable, "their" tonearm, "their" phono stage, "their" amplifier system and "their" loudspeakers in "their" test/listening room. It is not exact, only a recommendation based on what they heard in "their" test system. The upshot is it will be different/slightly different in everyone else's system.

If you have a solid state MC phono stage then selecting different resistive loadings can help "adjust" a cartridges response, particularly if it is hot in the treble (as most MC's have a rising HF response), but that is the only way you can make adjustments with solid state (putting a resister directive across the cartridge input) unless it is a MM stage and you connect an SUT in line.

With valve or tube electronics it more usual to use an SUT, and in this case the most important thing is to select the correct amount of gain for the cartridge to work correctly into the phono stage. Unless the cartridge has an extremely low internal impedance (usually have very low output too) then around 20dB of gain is sufficient (470 ohms load) for most MC's. Alternatively 26dB of gain (118ohms load) works well for lower output MC's and both will be fine for about 99% of MC cartridges.
Note: loading shown with SUTs is based on a phono stage input impedance of 47K ohms.
Click to expand...


That's very helpful. thanks a ton

Could you educate me a bit more on what 'numbers' to look for in an SUT?
I see 10x, 20x, etc.. Is it the output that I get from an SUT what really matters?
 
Darth Vader said:
Lower inductance types are more critical but higher inductance carts may need little if any tuning
Click to expand...
Surely the other way round. Lower inductance means fewer turns, lower source resistance and therefore lower output. It's the high output devices that don't work well with 100R and are affected by capacitive loading
 
Very interesting comments (chiefly G.T., Paskinn and Robert) that different resistances applied to MC cart's have little or no effect. This is NOT what I experience.

The number of times I've listened to my Urushi, Ebony or (more recently) Proteus for, say, half an hour and wondered what was wrong, only to realise I'd left the plug in place for another cart.

My Benz sounds 'orrible with 100 ohms but lovely with 220

My Vermillion degrades audibly above 100 ohms and likewise, it seems (it's a bit new !), my Transfig.

I think the internal loading is key here, as my K has about 4 ohms resistance and my Proteus only 1 ohm. The Benz is a bit higher.

The differences in external loading are not, i.m.e., subtle, let alone negligible, though as aforesaid, this may be influenced by ancillary kit and its revealing qualities.
 
banjoman said:
That's very helpful. thanks a ton

Could you educate me a bit more on what 'numbers' to look for in an SUT?
I see 10x, 20x, etc.. Is it the output that I get from an SUT what really matters?
Click to expand...

The gain of an SUT should be chosen based on the gain of your phono stage, the signal to noise of your phono stage and the overall gain of your system.

Typically if your MM phono stage has about 45dB-48dB of gain then:
  • an MC cartridge with an output between 0.3mV and 0.6mV a 1:10 (20dB) step up should suffice
  • an MC cartridge with an output between 0.1mV and 0.3mV a 1:20 (26dB) step up should suffice.
  • anything lower than 0.1mV and I would suggest an SUT with a custom wind specifically for your cartridge will yield the optimium results.
 
G T Audio said:
The gain of an SUT should be chosen based on the gain of your phono stage, the signal to noise of your phono stage and the overall gain of your system.

Typically if your MM phono stage has about 45dB-48dB of gain then:
  • an MC cartridge with an output between 0.3mV and 0.6mV a 1:10 (20dB) step up should suffice
  • an MC cartridge with an output between 0.1mV and 0.3mV a 1:20 (26dB) step up should suffice.
  • anything lower than 0.1mV and I would suggest an SUT with a custom wind specifically for your cartridge will yield the optimium results.
Click to expand...

That's very very helpful indeed. Thanks again
 
I had a Wood SL for 3 years had the loading on 100 ohms then tried it on 220 ohms I preferred the latter. However Benz recommended 120 ohms. I was using a Whest Audio 30R you just have to experiment and use the setting for two to three weeks at a time.

Regards,

Martin
 
davidsrsb said:
Surely the other way round. Lower inductance means fewer turns, lower source resistance and therefore lower output. It's the high output devices that don't work well with 100R and are affected by capacitive loading
Click to expand...

I am discussing low output MC carts here. The smaller the inductance the more pronounced the HF resonance peak and vice versa.

Inductance has 4 dependencies number of turns, coil length, coil area and magnetic permeability. Therefore construction plays a big part.

Cheers,

DV
 
I recently had the New Arkless 'super' MC valve hybrid phonostage on loan and I found cartridge loading to make a very clearly audible difference. I found that altering the loading on my own Paradise stage to make a clear difference too.
 
Jess (or is it Jez?) is using valves now? Well well.

I agree; loading options are not just for show, but I suppose they do compromise circuitry, and theoretically s.q., to some degree.
 
Jez - presumably Jeremy - not many men called Jess...

I don't think that loading options have to compromise sound quality - or at least, having the wrong loading definately does :).
 
YNWOAN said:
I recently had the New Arkless 'super' MC valve hybrid phonostage on loan and I found cartridge loading to make a very clearly audible difference. I found that altering the loading on my own Paradise stage to make a clear difference too.
Click to expand...

It doesn't surprise me on a solid stage phono stage that the difference is more audible. The main reason is because of the way of implementing the adjustment, which is by simply switching different value resistors across the incoming signal. These resistors, apart from normally being very cheap (just a few pence) can have a bigger influence because they sit directly across the signal path.
 
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